How to adjust flasing trim pot during board calibration

[xing]

Hi, I'm in the process of calibrating by PCIe1602/16 board, and in the GUI the instructions state to 1) first apply a certain voltage to a particular pin (e.g. 0 V to pin 37), 2) make certain connections (e.g. Ground to pin 18 and 19), and then 3) 'Adjust the flashing trim pot to within +/- 2 counts.' However, I do not know how to carry out the 3rd step. Do I need to click on something in the GUI? Or adjust something on the pin side? Or something else? Thanks.

Edited June 3 by xing
forgot to complete sentence

[DAQman]

The calibration is accomplished by adjusting potentiometers with a screwdriver. R1 adjusts the reference to the PGA amplifier, R3 adjusts the PGA output, and R2 is a gain adjustment. The schematic does not indicate a second gain adjustment. 

R4 adjusts the DAC 0 reference, R5 adjusts the DAC 0 offset, and R7 and R8 are for DAC 1.